Reducing aircraft noise is important to the growth of air transport and for improving the quality of life of people living near airports. The noise associated with an aircraft can be produced from various sources on the aircraft and by various mechanisms. For example, a fan of a turbofan aircraft engine can be a dominant source of noise during take-off and landing of an aircraft having modern high-bypass ratio turbofan aircraft engines.
The use of noise attenuating devices inside aircraft engines is known. Existing noise attenuating devices can be designed to achieve a desired acoustic performance. However, designing and manufacturing such noise attenuating devices to the specifications required to achieve the desired acoustic performance can be difficult, time-consuming and expensive.
Improvement is therefore desirable.